I am having trouble understanding how the 'by' function works. Using
this bit of code:
i <- data.frame(x=c(1,2,3), y=c(0,0,0),
B=c("red","blue","blue"))
j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=c('red','blue','green'))
plot(0, 0, type="n", xlim=c(0,4), ylim=c(0,1))
by(i, i$B, function(s){ points(s$x, s$y, col=s$B) })
by(j, j$B, function(s){ points(s$x, s$y, col=s$B) })
I would have expected the point at (1,1) to be coloured red. When
plotted, this row is indeed red:
> i[1,]
x y B
1 1 0 red
however, this next point is green on the plot even though I would like
it to be red:
> j[1,]
x y B
1 1 1 red
How can I achieve that?
Myles
The answer was (thanks to Mark Leeds) to do with the use of a factor instead of a vector. on [2017-08-05] at 08:57 Myles English writes:> I am having trouble understanding how the 'by' function works. Using > this bit of code: > > i <- data.frame(x=c(1,2,3), y=c(0,0,0), B=c("red","blue","blue")) > j <- data.frame(x=c(1,2,3), y=c(1,1,1), B=c('red','blue','green'))The use of I() prevents conversion to a factor: i <- data.frame(x=c(1,2,3), y=c(0,0,0), B=I(c("red","blue","blue"))) j <- data.frame(x=c(1,2,3), y=c(1,1,1), B=I(c('red','blue','green')))> plot(0, 0, type="n", xlim=c(0,4), ylim=c(0,1)) > by(i, i$B, function(s){ points(s$x, s$y, col=s$B) }) > by(j, j$B, function(s){ points(s$x, s$y, col=s$B) }) > > I would have expected the point at (1,1) to be coloured red. When > plotted, this row is indeed red: > >> i[1,] > x y B > 1 1 0 red > > however, this next point is green on the plot even though I would like > it to be red: > >> j[1,] > x y B > 1 1 1 red > > How can I achieve that? > > Myles
Putting answer here for future posterity. Didn't send to R-help initially
because I wasn't sure
what OP wanted. I guessed right. Sorry for confusion in thread.
GUESSING THAT YOU WANT IS BELOW
#==================================================================
i <- data.frame(x=c(1,2,3), y=c(0,0,0),
B=c("red","blue","blue"),
stringsAsFactors = FALSE)
j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=c('red','blue','green'),
stringsAsFactors = FALSE)
plot(0, 0, type="n", xlim=c(0,4), ylim=c(0,1))
points(i$x, i$y, col = i$B)
points(j$x, j$y, col = j$B)
On Sat, Aug 5, 2017 at 5:59 AM, Myles English <mylesenglish at gmail.com>
wrote:
>
> The answer was (thanks to Mark Leeds) to do with the use of a factor
> instead of a vector.
>
> on [2017-08-05] at 08:57 Myles English writes:
>
> > I am having trouble understanding how the 'by' function works.
Using
> > this bit of code:
> >
> > i <- data.frame(x=c(1,2,3), y=c(0,0,0),
B=c("red","blue","blue"))
> > j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=c('red','blue','green'))
>
> The use of I() prevents conversion to a factor:
>
> i <- data.frame(x=c(1,2,3), y=c(0,0,0),
B=I(c("red","blue","blue")))
> j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=I(c('red','blue','green')))
>
> > plot(0, 0, type="n", xlim=c(0,4), ylim=c(0,1))
> > by(i, i$B, function(s){ points(s$x, s$y, col=s$B) })
> > by(j, j$B, function(s){ points(s$x, s$y, col=s$B) })
> >
> > I would have expected the point at (1,1) to be coloured red. When
> > plotted, this row is indeed red:
> >
> >> i[1,]
> > x y B
> > 1 1 0 red
> >
> > however, this next point is green on the plot even though I would like
> > it to be red:
> >
> >> j[1,]
> > x y B
> > 1 1 1 red
> >
> > How can I achieve that?
> >
> > Myles
>
>
[[alternative HTML version deleted]]
... and, of course, by() should not be used at all for this sort of
thing in practice, as the "col" argument can be a vector. See
?plot.default if you you were not aware of this already.
j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=c("red","blue","green"),
stringsAsFactors = FALSE)
with(j,plot(x,y, col=B, xlim=c(0,4), ylim=c(0,1.2)))
Cheers,
Bert
Bert Gunter
"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Sat, Aug 5, 2017 at 2:59 AM, Myles English <mylesenglish at gmail.com>
wrote:>
> The answer was (thanks to Mark Leeds) to do with the use of a factor
> instead of a vector.
>
> on [2017-08-05] at 08:57 Myles English writes:
>
>> I am having trouble understanding how the 'by' function works.
Using
>> this bit of code:
>>
>> i <- data.frame(x=c(1,2,3), y=c(0,0,0),
B=c("red","blue","blue"))
>> j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=c('red','blue','green'))
>
> The use of I() prevents conversion to a factor:
>
> i <- data.frame(x=c(1,2,3), y=c(0,0,0),
B=I(c("red","blue","blue")))
> j <- data.frame(x=c(1,2,3), y=c(1,1,1),
B=I(c('red','blue','green')))
>
>> plot(0, 0, type="n", xlim=c(0,4), ylim=c(0,1))
>> by(i, i$B, function(s){ points(s$x, s$y, col=s$B) })
>> by(j, j$B, function(s){ points(s$x, s$y, col=s$B) })
>>
>> I would have expected the point at (1,1) to be coloured red. When
>> plotted, this row is indeed red:
>>
>>> i[1,]
>> x y B
>> 1 1 0 red
>>
>> however, this next point is green on the plot even though I would like
>> it to be red:
>>
>>> j[1,]
>> x y B
>> 1 1 1 red
>>
>> How can I achieve that?
>>
>> Myles
>
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